This invention relates to fuel cell systems and, in particular, to fuel cell systems which employ internal reforming.
In U.S. Pat. No. 4,532,192, assigned to the same assignee hereof, there is disclosed an internally reforming fuel cell system which is adapted to provide maximum utilization of the hydrogen fuel process gas. This is accomplished by incorporating in the system a transfer device which includes anode and cathode means and to whose anode means is fed the exhaust gas from the anode compartment of the fuel cell of the system. This exhaust gas typically comprises unused hydrogen, water, small amounts of carbon monoxide and methane (where methane is the fuel supply) and carbon dioxide.
As a result of applying a voltage across the anode and cathode means of the transfer device, the hydrogen in the applied exhaust is transferred to the cathode means of the device to the exclusion of the other constituents in the exhaust. This transferred hydrogen forms a first stream and this first stream is then combined with the methane fuel supply and the combined gases fed to the anode compartment of the fuel cell for steam reforming and electrochemical reaction.
The system of the '192 patent also makes use of the constituents remaining after extraction of the of the hydrogen. These constituents form a second stream which is first passed through a condenser to remove the water constituent. The removed water is then used to aid in the steam reforming process. This is accomplished by combining the water with the first stream and adding the combined gases to the methane fuel supply.
The second stream absent the water is then fed to a burner and burned with oxidant from the oxidant supply to remove any residual hydrogen. The resultant oxidant gas, which now includes substantial amounts of carbon dioxide, is then fed to the cathode compartment of the fuel cell as oxidant process gas.
The aforesaid system of the '192 patent is beneficial in realizing increased utilization of hydrogen in the fuel cell exhaust and in making use of the water and carbon dioxide in such exhaust in a manner which enhances system performance. However, the system requires the use of bulky condensers and heat exchangers which if eliminated or even reduced in size and number would further increase the benefits of the system.
It is therefore an object of the present invention to provide an improved internal reforming fuel cell system of the above type.
It is a further object of the present invention to provide an internal reforming fuel cell system of the above type in which the requirements for condensers and heat exchangers is reduced.